Some people have asked about why AdblockIE requires .NET 3.5. The short answer is that I wrote this addin for my own use, on my own machine, and on my machine I already have .NET 3.5.
The more technical answer is that I made some very limited use of .NET 3.5-only technologies--specifically, XML Linq. This comprises a total of maybe thirty lines of code, however, so it should only take someone familar with C# half an hour or so to rewrite for .NET 2.0.
I'll happily take a submitted patch that renders this 2.0 compatible. I don't, however, plan to do this myself. The time I can devote to this project is currently very limited, and I'd rather spend it adding cool new features and making AdblockIE more fast and reliable rather than rewriting the parts that rely on .NET 3.5. That's why it's open source, however--because you can change the source, submit patches, or fork it into a whole new project that does what you want.